Small room with many speakers. Use speakers with wide dispersion or narrow dispersion?

[HairyEars]

By the way, I saw that the 7382A subwoofer's amplifier is external and it has a fan. Is the fan loud? Can the amplifier be placed in-room without causing noise? Also, do Genelec's other subwoofers, such as the 7380A, also have fans or is it just the 7382A?

The fan is not audible and will kick in when the amp gets really hot; that is, when you play loud for an extended period of time. In a small room like yours, I suspect the demands on these monsters will minuscule and the fan mostly dormant.

External amps require good ventilation. You can read in the details in the Genelec user guide. Take that into account when you design your rack.

The other Genelec subwoofers don’t have fans and their amps are built-in.

 

[Kain]

Okay, thanks.

Here is a quick video of the room so you have a better idea of what it looks like. Please ignore the mess in the room. We are temporarily using it as a storage/study room right now.

As you can see, on one of the walls there is a built-in closet so I won't be able to wall mount speakers there. That is why I wanted to use stands for the surrounds. I don't mind placing speakers next to or in front of the closet doors. The TV is likely to be located on the wall where the red couch is because that side of the room is symmetrical (for the LCR speakers) and also because it would allow me to position the front L/R speakers out in the room as per your recommendation without blocking the entrance to the room. Also, the window you see in the room does not extend all the way to the floor.

By the way, does room symmetry matter for speakers? I am assuming it does. It would be better for the LCR speakers and TV to be on the side of the room that is symmetrical (wall where the red couch is), correct? The wall opposite of the red couch is not 100% symmetrical because of the short pathway to the door.

 

[Kain]

Genelec's monitor placement guide: https://www.genelec.com/monitor-placement

Genelec recommends placing the monitor at a minimum of 5 cm from the front wall and at a max of 60 cm from the front wall. Is this when you don't have a subwoofer? In the second quote below, Genelec recommends placing the monitor at a distance of greater than 1.1 meters (if you have a subwoofer). So, if you have a subwoofer, place the L/R speakers away from the front wall and if you don't have a subwoofer, place them close to the wall?

I also noted the following from the guide:

"The first solution is to flush mount the monitors into a hard wall (creating a very large baffle) eliminating the rear wall reflections and therefore cancellations. Another possibility is to place the monitor very close to the wall minimising the gap. This raises the lowest cancellation frequency so high that the monitor has become forward-directing, and the cancellation no longer occurs. Remember that the low frequency boost should be compensated for when the monitor is mounted close to the wall (up to +6 dB gain)."

So, as highlighted above, they are saying you can place the monitors close to the (front) wall to get rid of cancellation dips and compensate for (other) boosted low frequencies through room correction?

Wall Reflections and Cancellations

The distance from the wall where the monitors are placed can be very significant to the quality of sound. When there is a gap between the monitor and the wall, at the frequency where this distance is equal to one quarter of the sound wavelength, the wall reflection is out of phase with the monitor, and the reflected audio cancels the audio from the monitor. At this frequency, the sound level is reduced. How much reduction occurs depends on the distance and on how much sound the wall behind the monitor reflects.

Wall reflections or back reflections generate a set of cancellations at different frequencies (also called comb filtering). The first cancellation notch can be between 6 dB and 20 dB deep. Equalization of the monitor output level does not help, as the same level change applies also to the reflected sound.

The first solution is to flush mount the monitors into a hard wall (creating a very large baffle) eliminating the rear wall reflections and therefore cancellations. Another possibility is to place the monitor very close to the wall minimising the gap. This raises the lowest cancellation frequency so high that the monitor has become forward-directing, and the cancellation no longer occurs. Remember that the low frequency boost should be compensated for when the monitor is mounted close to the wall (up to +6 dB gain).

Alternatively, the monitor could be moved considerably further away from the wall to eliminate back reflections. The cancellation frequency will be lowered below the low frequency cut-off of the monitor. When the monitor is moved away from the walls, it also moves close to the listener. This increases the direct sound level and reduces the reflected sound level which improves the sound quality.

Acoustical treatment of the walls is another solution. It could mean modifying the wall and making it very absorptive so that the amplitude of the reflected energy is small and does not cancel the direct sound. When a subwoofer is used to reproduce low frequencies the monitors can be placed more freely. The subwoofer(s) should be placed close to the wall(s). The monitors could be placed at distances where low frequency notches do not occur in their pass-band.

See also the special section on Acoustics for more options for tuning and calibrating your Genelec monitors, to further improve the sound quality.

To avoid cancellation of audio because of the sound reflecting back from the wall behind the monitor, follow the placement guideline pictured below. The wall reflection happens at relatively low woofer frequencies only. Avoiding the cancellation is important because the reflected sound can reduce the woofer output causing the monitor low frequency output to appear to be too low, thus resulting e.g. on mistakes in the final mix in music production. To avoid the cancellation, place the monitor close enough to the wall. Typically the distance from the monitor front to the wall should be less than 60 centimetres. This ensures that the low frequency output is not reduced. Additionally, the monitor needs a minimum clearance of 5 cm to the wall to ensure full output from the rear bass reflex port.

Typical recommended distances from the wall behind monitors and subwoofer are shown in the picture below.

 

[HairyEars]

Genelec's monitor placement guide: https://www.genelec.com/monitor-placement

Genelec recommends placing the monitor at a minimum of 5 cm from the front wall and at a max of 60 cm from the front wall. Is this when you don't have a subwoofer? In the second quote below, Genelec recommends placing the monitor at a distance of greater than 1.1 meters (if you have a subwoofer). So, if you have a subwoofer, place the L/R speakers away from the front wall and if you don't have a subwoofer, place them close to the wall?

I also noted the following from the guide:

"The first solution is to flush mount the monitors into a hard wall (creating a very large baffle) eliminating the rear wall reflections and therefore cancellations. Another possibility is to place the monitor very close to the wall minimising the gap. This raises the lowest cancellation frequency so high that the monitor has become forward-directing, and the cancellation no longer occurs. Remember that the low frequency boost should be compensated for when the monitor is mounted close to the wall (up to +6 dB gain)."

So, as highlighted above, they are saying you can place the monitors close to the (front) wall to get rid of cancellation dips and compensate for (other) boosted low frequencies through room correction?

​

I discussed it in this post here:

Permit me to give you one more tip:

As you may be well aware, your most important speakers are the left and right. For that reason, as a first step, I would purchase only the LRC + the subs and experiment with their position. It’s quite commen that the L/R sound might best when their face is 1.1m or more away from the rear wall. Note that the room rear wall cancellation frequency is shifted to 2 lower octaves, which is played by the subwoofers.

Only after that all-important fact is established, should you determine where your surrounds are placed.

In my small room, for example, given that my monitors are 1.3m away from the rear wall, I don’t have enough space for wide speakers. Likewise, 6 height speakers are just too many in regards to my sitting position and the rear wall.

It’s better to have great L/R placement in 7.1.X than a 9.1.6 with suboptimal L/R placement.

Which approach sounds better in your room requires experimentation (repeating myself).

 

[HairyEars]

Okay, thanks.

Here is a quick video of the room so you have a better idea of what it looks like. Please ignore the mess in the room. We are temporarily using it as a storage/study room right now.

As you can see, on one of the walls there is a built-in closet so I won't be able to wall mount speakers there. That is why I wanted to use stands for the surrounds. I don't mind placing speakers next to or in front of the closet doors. The TV is likely to be located on the wall where the red couch is because that side of the room is symmetrical (for the LCR speakers) and also because it would allow me to position the front L/R speakers out in the room as per your recommendation without blocking the entrance to the room. Also, the window you see in the room does not extend all the way to the floor.

By the way, does room symmetry matter for speakers? I am assuming it does. It would be better for the LCR speakers and TV to be on the side of the room that is symmetrical (wall where the red couch is), correct? The wall opposite of the red couch is not 100% symmetrical because of the short pathway to the door.

You’re correct, the red sofa area is the best location for your TV/mains.

You should treat the windows and closet opposite. Mount panels over the surfaces and forgo their intended functionality. If not, the sound will take a big hit.

Plan on vertical heavy bass traps in the red sofa area’s corners. It’s highly recommended to install bass traps along the corners where the ceiling meets the walls.

Again, I feel your envisioned monitors are too powerful for such a small space. Your subs could be 7370 x 2—and even that might be an overkill—certainly, not larger than 7380 x 2. The heights should be 8341. You could use 8351 for LCR, depending how close you are to the mains. 8341 Would competently serve as surrounds. The SPL of this proposed system, which you might consider “small,” is insane; you’ll never scratch its limits.

If you went with small subs and stationed them by your sides, you could build a frame around them and place the side surrounds on them. That would save you some space. See attached photo with a similar frame I built for my 7350. The rear surrounds can be mounted on the wall behind you. Only the wides will require stands, should you choose to add them.

 

[Kain]

Thanks.

Do Genelec's ceiling mounts for the 8341A and 8351B work on concrete ceilings? If yes, I assume they come with everything that I would need to mount the 8341A or 8351B to the ceiling? Also, are there any special precautions or advice that I should take to make sure the speakers don't fall down or are the Genelec ceiling mounts plenty sturdy?

 

[HairyEars]

Thanks.

Do Genelec's ceiling mounts for the 8341A and 8351B work on concrete ceilings? If yes, I assume they come with everything that I would need to mount the 8341A or 8351B to the ceiling? Also, are there any special precautions or advice that I should take to make sure the speakers don't fall down or are the Genelec ceiling mounts plenty sturdy?

Genelec's mounts are ideal for concrete surfaces and come complete with all the accessories required to mount the monitors, other then the plugs and bolts,

Here's a wall mount:

8000-402 Wall mounting bracket - Genelec.com

Adjustable wall mounting bracket.

www.genelec.com

Celing mount:

8000-436B/W Short ceiling mount - Genelec.com

Short ceiling mount for all 8000 series and G series models.

www.genelec.com

There are other other options in Genelec's catalog. Give it a gander.

The ceiling mounts are sturdy; the weak link is always the plugs and bolts. This is another reason I'd prefer to mount 8341A on the ceiling. The smaller are are quite lighter vis-a-vis the 8351B (9.8kg vs 14.3kg(

 

[Kain]

Hopefully my last question. You've been a great help, thanks a lot for that.

Since the wall with the red sofa is probably the best for the TV and LCR speakers (which you agreed to), you recommended I place vertical bass traps along the two corners of that wall. Do they have to extend from the floor till the ceiling (meaning covering the whole corner)? I am just asking because, as you can see in the room video above, there is an A/C vent near the corner of one of the walls which I wouldn't want to cover up (either partially or wholly). Would I use relatively "not so wide" or big bass traps but still have them extend from the floor to the ceiling in the corners? Or would I use bass traps that cover the majority of the corners but not fully from the floor to the ceiling?

Lastly, should I also use diffusion panels or just absorption panels all over the room? Should I install absorption panels on the ceiling as well? I am assuming I would want to make the room quite acoustically dead (which would mean installing absorption panels on the back wall, closet doors, front wall, and parts of the wall that has the window and maybe on the windows themselves).

 

[HairyEars]

I’ll answer your questions, but what I’m offering are merely morsels, some of which are based on my opinions solely. At this point, it’s best if you devoted yourself to studying room acoustics and sound treatment—at least to the point you’re comfortable with your decisions.

Bass traps have to be symmetrical; that is, in pairs, one facing the other. Otherwise, they don’t work effectively.

They should be big and thick: 50cm x 50cm x 50cm, or a bit less, is a good size.

Don’t use small traps. If partially blocking the vent is unacceptable, go from the floor up to that area.

You can never have enough bass traps. If possible, mount some where the ceiling meets the walls (see attached photos). Again, in pairs, facing each other.

In such a small room, you usually mount a diffuser only behind your back. Don’t use a thin board with cuts in it; it’s not effective. Purchase a parametric or QD diffuser. Check out my photos. If you don’t have the budget, use an absorber. It works pretty well in a small room too.

You definitely want to install absorber panels on the wall behind the monitors and your side walls. Yes, cover the windows and closet. The more exposed glass in the reflection zone, the worse the sound.

A cloud is indispensable for a great sound. I have two clouds installed in parallel—4 boards and 2 boards respectively. My ceiling is sheetrock so I mounted them using metal cables. If you have a concrete ceiling, you can fix them to the surface. An air gap equal to the thickness of the panel is helpful.

My treatment is not particularly handsome, but it’s quite effective. In your country, you can probably source nicer materials with more flawless execution. Still, make sure they perform. There’re vendors that put too much emphasis on beauty and less on functionality.

 

[Kain]

Okay, thanks.

And a carpeted floor is not recommended, correct? I've seen the earlier post by you in this thread and also other people online where they say carpets should be avoided. I have a tiled floor and I assume I should leave it as it is?

 

[HairyEars]

A rug should be avoided, but tiles would give you terrible reflections. Can you install hardware floor?
Personally, I would take a rug over tiles, but not happily.

 

[Kain]

I'll see if installing a hardwood floor is an option but I could also install a carpet over the entire tiled floor.

So, you would prefer it like this?:

Hardwood floor > carpeted floor > tiled floor.

Are hardwood floors the best for audio setups?

 

[HairyEars]

I'll see if installing a hardwood floor is an option but I could also install a carpet over the entire tiled floor.

So, you would prefer it like this?:

Hardwood floor > carpeted floor > tiled floor.

Are hardwood floors the best for audio setups?

Hardware floors are considered best practices by professional studios. I haven't seen any science behind it, but I read science against a rug.

 

[dagfinn]

Hardware floors are considered best practices by professional studios. I haven't seen any science behind it, but I read science against a rug.

I don't understand why you want HF floor relections? A hard floor will do that... And as your guy in the video shows, even a thin one helps. A thick one helps more. What's the science against?

 

[HairyEars]

I don't understand why you want HF floor relections? A hard floor will do that... And as your guy in the video shows, even a thin one helps. A thick one helps more. What's the science against?

A carpet helps reduce the floor reflections, but the expert in the video is very much against it.

A quote:

“Putting such a large surface area of high frequency absorber means taking away a lot of the energy at those high frequencies available in your room. We can look at a carpet as a very thin, poorly performing, high frequency absorber.”

According to him, the carpet has zero chance at doing anything about the first dip, which is the most important one. He uses this simplified calculator the make his point:
https://mehlau.net/audio/floorbounce/

He goes on to say that the effect that the carpet has is to severely reduce high frequency reverb, without actually improving the sound of your speakers, and, “a carpet steals our limited resources of high frequency, without giving us anything in return.”

Perhaps you want to watch that video again.

 

[dagfinn]

Ok, pardon me for not agreeing with the expert, I think a carpet can improve the sound in the room. The properties of "carpet" is highly variable, but even the one he presents does some of the job I require - reduce HF reflections. HF resonating in the room is unpleasant to me, and if you measure it, it's a mess. Lost energy? I prefer direct over reflected for many reasons, like imaging. Of course, in a well treated/designed studio room you may already have very dead walls and ceiling, which changes the acoustic situation and maybe a little floor is ok. But there are many floors and carpets, and a heavy carpet can even reduce modes in a bad floor. So saying "carpets are bad" in general, I think is misleading.

 

[HairyEars]

With all due respect, the discussion isn't about your particular situation.

The video is in the context of a well-treated room, used for music production, and how to deal with floor reflections. His recommendation, wrapped in a clear exposition and espoused by pro studios, is to have a bare hardware floor.

Incidentally, the OP intends to acoustically treat his room as best he can, so that recommendation is relevant to him.

 

[Kain]

Quick question:

If my goal is to hear as much direct sound as possible by treating my room the best I can, what is the purpose of floor reflections and why would I want them? A carpet is a high-frequency absorber; but that is for reflections, correct? Wouldn't a carpet help me hear more direct sound even in a well-treated room?

 

[NTK]

Quick question:

If my goal is to hear as much direct sound as possible by treating my room the best I can, what is the purpose of floor reflections and why would I want them? A carpet is a high-frequency absorber; but that is for reflections, correct? Wouldn't a carpet help me hear more direct sound even in a well-treated room?

Quoting Dr Toole:

...​

There is little experimental evidence that I am aware of relating to vertical directivity. There is no doubt that ceiling floor reflections are audible, but the best designed experiment I know of indicated that listeners were not happy when the floor reflection was removed. Humans have evolved with a hard reflective surface always under their feet. Section 7.4.7 in the 3rd edition discusses it. The folklore, though, is extensive.​

...​

Blind Listening Test 2: Neumann KH 80 vs JBL 305p MkII vs Edifier R1280T vs RCF Arya Pro5

My take as I've done many times, speakers that exaggerate the pattern on/off-axis may sound harsh while speakers with inverted pattern sound smoother. How can a speaker exaggerate the pattern on-axis?

www.audiosciencereview.com

 

[Kain]

Thanks.

How come most, if not all, commercial movie theaters I've been to have carpeted floors?